Improvement on a Multi-Channel Broadcast Encryption Scheme

Abstract

Broadcast encryption provides a convenient method to distribute digital content to subscribers over an insecure broadcast channel so that only the qualified users can recover the data. In some broadcast encryption based systems such as pay-TV, multiple ciphertext headers (via multiple channels) are needed since the sender needs to send various contents to different groups of subscribers. Each receiver needs to store all headers in order to switch channel fluently. Recently, Phan et al. described a multi-channel broadcast encryption scheme, in which the sender encapsulates multiple ephemeral keys into one ciphertext header so that each receiver only stores one ciphertext header and still can recover various ephemeral keys for different contents. We present an improvement on their scheme, which will reduce the size of public key and the computation cost for decryption. The improved scheme can be used to construct efficient dynamically privileged broadcast encryption system.